Imaging of cells and particles in a sample fluid stream can be used to identify the cells and particles and determine whether an individual is healthy or is suffering from illness or disease. To gather the necessary information from the images, the focusing of the image capture device must be precise. Currently available methods for focusing systems have either relied on manual focusing or utilized markers on side of the fluid stream to focus. Existing systems, however suffer from the inability to maintain focus and actually focus on the item being captured in the image. Therefore, improved methods and systems are needed.